Does The CT Scan Show Acoustic Neuroma?
Computed tomography (CT) scan is useful in diagnosing acoustic neuroma but small acoustic neuroma tumors might not be visible clearly from a CT scan. A large acoustic neuroma tumor is seen as a homogenous enhancement and can be seen well from a CT scan. The contrast-enhanced CT scan is more accurate in detecting acoustic neuroma tumors than the normal CT scan however, tumors less than 1 cm are difficult to visualize even with contrast CT scans. Therefore, in those cases air or gas CT cisternography is needed to identify small tumors, false negatives can occur if there are arachnoid adhesions or if the internal acoustic canal is very narrow. The radiation exposure in CT scan is quite high and contrast CT scan needs contrast injection has the risk of an allergic reaction. MRI is better in diagnosing acoustic neuroma tumors than a CT scan or contrasts CT scan as the lesions are seen clearly and there is no radiation exposure. Some patients cannot undergo an MRI scan if they have metal implants or metal shrapnel, in that case, a CT can be done. (1)
How Do They Remove An Acoustic Neuroma?
The main treatment modality of acoustic neuroma is the removal of the tumor. The whole tumor or part of the tumor can be removed depending on the size, location and hearing loss, your doctor will decide which approach is more suitable for you. There are mainly 3 surgical approaches for removal of acoustic neuroma tumor
Translabyrinthine: An incision is made behind the ear and the bone behind the ear and some parts of the middle ear is removed. This procedure is usually used for tumors that are larger than 3 cm. The main advantage of this procedure is that the facial nerve can be seen therefore, damage to the nerve can be avoided. Also, the recurrence rate is nil. The main disadvantage is permanent hearing loss. The intraoperative mortality rate is 0-2% in this procedure.
Retrosigmoid/ Sub-Occipital: In this procedure, the approach is through the back of the skull and the back of the tumor is exposed here. Here, a tumor of any size can be removed while preserving the hearing function. The mortality rate is about 0.5% for small tumors excised in this approach.
Middle Fossa: In this procedure, a small part of the skull bone above the ear is removed to access the ear canal. Small tumors in the internal auditory canal which is a narrow passageway can be removed. The hearing function also can be preserved to a significant level from this procedure. The mortality rate is also 0%.
The near-total or subtotal removal of the tumor has a regrowth rate of 21-22% and further treatment is required in 2-10% of cases. Even with the removal of the whole tumor, there is a recurrence rate of 2.4-3%. (2) (3) (4)
What Is The Complication Of Surgery?
- Permanent hearing loss
- Arterial injury – damage to the posterior inferior cerebellar artery
- Cerebellar injury
- Facial paralysis
- Cerebrospinal fluid complications – sometimes temporary postoperative hydrocephalus can occur
Computed tomography (CT) scans are useful in diagnosing acoustic neuroma but small acoustic neuroma tumors might not be visible clearly from a CT scan. The contrast-enhanced CT scan is more accurate in diagnosing acoustic neuroma tumors however lesion less than 2 cm can be difficult. A large acoustic neuroma tumor is seen as a homogenous enhancement and can be seen well from a CT scan. The radiation exposure in CT scan is quite high and contrast CT scan needs contrast injection has the risk of an allergic reaction. The main treatment modality of acoustic neuroma is the removal of the tumor. The whole tumor or part of the tumor can be removed depending on the size, location and hearing loss. There are mainly 3 surgical approaches for removal of acoustic neuroma tumor: translabyrinthine, retrosigmoid/ sub-occipital, middle fossa.
The mortality rate is high and there is a risk of permanent hearing loss with translabyrinthine approach. Retrosigmoid carries a mortality rate of 0.5% and the middle fossa mortality rate is 0%.
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